Chapter 139:10Chanukah

10. The time to kindle [the Chanukah lights] is immediately after the
appearance of three stars and not later (1). It is forbidden to engage in
any activity, even Torah study, before kindling them (that is, once the
time for lighting has arrived). If, however, one has not recited the
evening service [before the appearance of three stars], one should pray
first and then light them (2).

Before kindling the lights, one should gather all the members of one's
family so that they become aware of the kindling ("pirsumei milsah").
Enough oil should be placed [in the menorah] so that the lights will burn
for at least half an hour (3).

After the fact, if one did not light immediately (at the correct time), one
may light with a blessing [throughout the entire night (4)] as long as the
members of one's household are awake. If, however, the members of one's
household have already gone to sleep, there is no opportunity to "publicize
the miracle" ("pirsumei nisah"). Therefore, one should light without
reciting a blessing (5).

A person who will not have the opportunity to kindle [the Chanukah lights]
at night, may do so beforehand, kindling them any time after "plag
haminchoh", that is, an hour and fifteen minutes before the appearance of
the stars. (This time period is measured according to the concept of
"sho'os zemanios" ("seasonal hours"), which are calculated according to the
length of daylight (6) (see Chapter 69, Law 2). During Chanukah, when the
days are short, if the daylight lasts ten sixty-minute hours on the clock,
"plag haminchoh" begins an hour and two-and-a-half minutes before the
appearance of the stars).

[When kindling the Chanukah lights before nightfall,] one must be careful
to place enough oil [in the menorah] for them to burn until a half hour
after the appearance of the stars. If they [are not fit to] burn that long,
one has not fulfilled the mitzvah (7).

FOOTNOTES:

(1) The Talmud states that the mitzvah is to light "with sunset" and there
is a dispute among the "rishonim" (early authorities) as to what precisely
this means. Some say it means the beginning of sunset (that is, when the
sun firsts disappears under the horizon), while others say that it means
the end of sunset, that is, the appearance of three stars (See Mishna
Berura 671:1).

(2) The more frequently occurring mitzvah ("todir") usually comes first.
Furthermore, we recite the "Shema," which is a Torah obligation, during
Maariv (evening service), whereas lighting the Chanukah candles is rabbinic
in origin. Those who usually pray Maariv after the appearance of three
stars, should preferably light the Chanukah candles before Maariv (that is,
before the appearance of the stars) (Ibid.)

(3) Those who light at the beginning of sunset (see note (1)), should be
careful to have enough oil to burn for at least half an hour after the
appearance of three stars.

(4) Lighting after daybreak is not a fulfillment of the mitzvah.

(5) Although it is preferable to have two or three family members awake
during the time of lighting, if one adult male or female, or even a child
with some understanding, is awake, one may light with a blessing. The
blessing is recited only when the mitzvah is being performed in the way it
was intended by the Sages. Since the entire purpose of the mitzvah to light
Chanukah candles is to publicize the miracle that occurred, if one is not
lighting outside or at a window where the public can see it, or inside the
house at a time when the household members will see it, then one is not
fulfilling the mitzvah completely in the way it was intended, and therefore
one should not recite the blessing over the mitzvah.

(6) The length of each "seasonal hour" is calculated by totaling the number
of minutes from dawn ("alos ha'shachar") until the appearance of 3 stars
("tzeis ha'kochavim"), and then dividing it by twelve (some say from
sunrise to sunset).